Members of modern society are confronted with a wide variety of circumstances that may diminish their mental and emotional well-being. For example, stress is a major problem in modern society. Sometimes people are aware of being under stress, whereas other times they are not. Some long-term conditions with high stress can be chronic, and people may be less likely to notice whether they are under high stress or may be generally less sensitive to stressors. Stress can impact all members of society, including those who operate large commercial vehicles, such as aircraft, buses, trucks, trains, ships, etc.
Vehicle accidents, particularly those involving large commercial vehicles, can result in catastrophic loss of lives and property. Such accidents can be caused by a variety of contributing factors, including the emotional state of the vehicle operator. For example, many plane crashes have been caused in part by pilot error, which is more likely to occur if the pilot is operating the aircraft in a compromised emotional state. In some cases, post-crash investigations have uncovered evidence that a pilot was suffering from stress, depression, mental illness, sleeplessness, fatigue, or other diminished capacities. Because vehicle accidents can be quite devastating, it is desirable to minimize the likelihood of an accident using every means possible.